” Synergy lets you easily share a single mouse and keyboard between multiple computers with different operating systems, each with its own display, without special hardware. It’s intended for users with multiple computers on their desk since each system uses its own monitor(s).
Redirecting the mouse and keyboard is as simple as moving the mouse off the edge of your screen. Synergy also merges the clipboards of all the systems into one, allowing cut-and-paste between systems. Furthermore, it synchronizes screen savers so they all start and stop together and, if screen locking is enabled, only one screen requires a password to unlock them all. Learn more about how it works. Synergy is open source and released under the GNU Public License (GPL).  ”. Introduction from official SourceForge site http://synergy2.sourceforge.net .

Tutorial:
BMHO, Synergy is not new kid on the block, but it’s still a great open source tool and I’ve been using it for few months now. Since I had to upgrade my laptop to Windows 7, I’ve wrote this little tutorial to make sure that I wouldn’t forget something
I will assume that you have a desktop on the right side (which will play a server role) and a laptop computer on the left side (which will play a client role) and that they are both connected to the same LAN.

So, let’s do it. Here’s quick tutorial with few simple steps:
1. Install Synergy on Server and Client computer (e.g. deskop and laptop).
2. Configure Client - open Synergy and choose option Use Another Computer’s Shared Keyboard and Mouse (client), and enter other computer’s Host name (Server’s Network name e.g. computer1.domain.net). Now click Advanced and give your client computer apropriate screen name (e.g. laptop) 
3. Configure Server - open Synergy and choose option Share this computer’s keyboard and mouse (server). Now click Advanced and give your server a screen name (e.g. master).
4. Now comes the tricky part. Click the Screens & Links Configure button on the Server. Under Screens Add both laptop and master screens and leave all the options in their default values. Under Links add two links: 
a) “master is right of laptop” - 0 to 100% of the right of laptop goes to 0 to 100% of master.
b) “laptop is left of master” - 0 to 100% of the left of master goes to 0 to 100% of laptop. 
5. Configuration is finsihed. Now click the Start button on the server and then click it on the client computer. You should be able to use mouse and keyboard on both computers just like when working on extended desktop. Enjoy!